|I hate to seem contentious but you're mistaken T-R-A|
Typical overhead in a network connection is about 15-20%. Which is to say, you can expect to get 80% of your rated bandwidth.
If you have questions about your external connection, you really need to contact your provider. They can answer your question. What I can tell you is a T3 in North America should be more along the lines of 45 Mbps.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.